The investigators reported that treating mice with an extract of leaves of Ginkgo biloba both before and after implanting human breast or brain (glioma) tumours decreased expression of a cell receptor associated with invasive cancer. This decreased expression slowed the growth of the breast tumours by 80 percent as long as the extract was used, compared to untreated mice, and also reduced the size of the brain tumours, but temporarily, and to a lesser extent.

"It is very encouraging that Ginkgo biloba appeared to reduce the aggressiveness of these cancers, because it suggests that the leaves could be useful in some early stage diseases to prevent them from becoming invasive, or spreading," said the study's senior author, Vassilios Papadopoulos, DPharm, PhD, Director, Biomedical Graduate Research Organization and Associate Vice President of Georgetown University Medical Center.

"But I must stress that this is a study in mice, and so we cannot say what anticancer effects, if any, Gingko biloba might offer humans," he said.

The researchers became interested in Gingko biloba because their research suggested that it might interact with the peripheral-type benzodiazepine receptor (PBR), a molecule they have been studying for the last 20 years. For example, they have determined that this protein is involved in bringing cholesterol into a cell's mitochondria.

So they looked at whether cancer cells produce more of these cholesterol-bearing receptors, and found that some highly invasive cancers do, indeed, over-express PBR. They selected breast cancer cells that over-expressed PBR, implanted them in mice, and treated the mice with a standardized extract of Ginkgo biloba leaves. After 30 days, tumor size was reduced by 35 percent, compared to untreated mice.